In recent years, fuel cell modules including a cell stack having a plurality of fuel cells arranged inside a housing container that are capable of generating power using fuel gas (gas containing hydrogen) and air (oxygen-containing gas) have been proposed as forms of next-generation energy. Various fuel cell devices including the fuel cell modules in an exterior case have been proposed.
Various kinds of fuel cells such as polymer electrolyte fuel cells (PEFC), molten-carbonate fuel cells (MCFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and the like are known as such fuel cells; however, in particular, solid oxide fuel cells may easily follow partial loads for household use.
The partial load operation is generally known to decrease the amount of fuel gas supplied to the cell stack (fuel cells).
However, during the partial load operation of the fuel cell device, a rate of fuel utilization and amount of current (electric power generation) of the cell stack fluctuate (declined compared to during the rated operation) according to an external load.
Therefore, there is a need for a more efficient fuel cell device with improved operating conditions during the partial load operation.